LED sidewall processing to mitigate non-radiative recombination

ABSTRACT

LEDs and methods of forming LEDs with various structural configurations to mitigate non-radiative recombination at the LED sidewalls are described. The various configurations described include combinations of LED sidewall surface diffusion with pillar structure, modulated doping profiles to form an n-p superlattice along the LED sidewalls, and selectively etched cladding layers to create entry points for shallow doping or regrowth layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a U.S. National Phase Application under 35U.S.C. § 371 of International Application No. PCT/US2016/066700, filedDec. 14, 2016, entitled LED SIDEWALL PROCESSING TO MITIGATENON-RADIATIVE RECOMBINATION which claims the benefit of priority of U.S.Provisional Application No. 66/271,189 filed Dec. 22, 2015, both ofwhich incorporated herein by reference.

BACKGROUND Field

Embodiments described herein relate to light emitting diodes (LEDs).More particularly, embodiments relate to LED structures to mitigatenon-radiative recombination at the LED sidewalls.

Background Information

Flat panel display panels are gaining popularity in a wide range ofelectronic devices ranging from mobile electronics, to televisions andlarge outdoor signage displays. Demand is increasing for higherresolution displays, as well as for thinner, lighter weight, and lowercost electronic devices with larger screens. Conventional organic lightemitting diode (OLED) technologies feature emissive organic layers overa thin film transistor (TFT) substrate. Conventional liquid crystaldisplay (LCD) technologies feature a liquid crystal layer over a TFTsubstrate, and a backlighting unit. More recently, it has been proposedto incorporate emissive inorganic semiconductor-based micro LEDs intohigh resolution displays.

SUMMARY

Embodiments describe light emitting structures (e.g. LEDs) and methodsof forming light emitting structures (e.g. LEDs) with various structuralconfigurations to mitigate non-radiative recombination at the lightemitting structure (e.g. LED) sidewalls. In some embodiments, the lightemitting structure configurations combine light emitting structuresidewall surface diffusion to mitigate carrier diffusion to the lightemitting structure surfaces, with pillar structures for internallyconfining the current injection region. In some embodiments, lightemitting structures include modulated doping profiles within a claddinglayer and sidewall dopant profiles to form an n-p superlattice along thelight emitting structure sidewalls. In some embodiments, light emittingstructures include selectively etched cladding layers to create entrypoints for shallow doping or regrowth layers.

In an embodiment, a light emitting structure (e.g. LED structure)includes a body (e.g. an LED body), which includes a first (e.g. top)cladding layer doped with a first dopant type, a barrier layer (e.g.bottom barrier layer), and an active layer between the first claddinglayer and the barrier layer. In such an embodiment, a pillar structureprotrudes from a first (e.g. bottom) surface of the body, and the pillarstructure includes a second (e.g. bottom) cladding layer doped with asecond dopant type opposite the first dopant type. The light emittingstructure may further include a confinement region including a dopantconcentration spanning sidewalls of the body and the first surface ofthe body. In an embodiment, the dopant concentration is formed of thesecond dopant type and encroaches from the sidewalls of the body towarda center vertical axis of the light emitting structure and from thefirst surface of the body toward the active layer, and the dopantconcentration laterally encroaches toward a center vertical axis of thelight emitting structure within the body past sidewalls of the pillarstructure. For example, the dopant concentration may encroach from thesidewalls of the body toward the center vertical axis and from thebottom surface of the body toward the active layer. The dopantconcentration may also encroach laterally above sidewalls of the pillarstructure within the body toward the center vertical axis.

In an embodiment, the pillar structure protrudes from a surface (e.g.bottom surface) of the barrier layer, the confinement region dopantconcentration spans the surface (e.g. bottom surface) of the barrierlayer, and the dopant concentration encroaches laterally toward thecenter vertical axis within the barrier layer past the sidewalls of thepillar structure. For example, the dopant concentration may encroachlaterally within the barrier toward the center vertical axis and abovethe sidewalls of the pillar structure.

In an embodiment, the first dopant type is n-type, the second dopanttype is p-type, and the dopant concentration is formed of a Mg or Zndopant. In an embodiment, a conformal passivation layer is formed on andspans the sidewalls of the body, the sidewalls of the pillar structure,and a surface (e.g. bottom surface) of the pillar structure opposite thebody. An opening may be formed in the conformal passivation layer on thesurface of the pillar structure, and a conductive contact (e.g. bottomconductive contact) formed on the surface (e.g. bottom surface) of thepillar structure and within the opening of the conformal passivationlayer.

In an embodiment, the dopant concentration encroaches further toward thecenter vertical axis within the barrier layer (e.g. bottom barrierlayer) than within the active layer and the first (e.g. top) claddinglayer. The light emitting structure may further include a base (e.g. topbase) including a first (e.g. bottom surface), and the body protrudesfrom the first surface of the base, and the first surface of the base iswider than the body. The dopant concentration may span the first (e.g.bottom) surface of the base (e.g. top base), and encroach toward asecond (e.g. top) surface of the base opposite the first (e.g. bottom)surface of the base. A second (e.g. top) conductive contact may beformed on the second (e.g. top) surface of the base. In an embodiment,the conductive contact (e.g. bottom conductive contact) is bonded to acontact pad on a display substrate with a solder material.

In an embodiment, the dopant concentration encroaches further toward thecenter vertical axis within the barrier layer (e.g. bottom barrierlayer) and within the active layer than within the first (e.g. top)cladding layer. The light emitting structure may further include a base(e.g. top base) including a first (e.g. bottom surface), and the bodyprotrudes from the first surface of the base, and the first surface ofthe base is wider than the body. The dopant concentration may span thefirst (e.g. bottom) surface of the base (e.g. top base), and encroachtoward a second (e.g. top) surface of the base opposite the first (e.g.bottom) surface of the base. A second (e.g. top) conductive contact maybe formed on the second (e.g. top) surface of the base. In anembodiment, the conductive contact (e.g. bottom conductive contact) isbonded to a contact pad on a display substrate with a solder material.

In an embodiment, a light emitting structure (e.g. LED structure)includes a body (e.g. an LED body), which includes a first (e.g. top)cladding layer doped with a first dopant type, a second (e.g. bottom)cladding layer doped with a second dopant type opposite the first dopanttype, and an active layer between the first cladding layer and thesecond cladding layer. A confinement region including a dopantconcentration may span sidewalls of the first (e.g. top) cladding layer,the active layer, and the second (e.g. bottom) cladding layer, where thedopant concentration encroaches from the sidewalls of the first claddinglayer, the active layer, and the second cladding layer toward a centervertical axis of the light emitting structure. In an embodiment, thefirst dopant type is n-type, the second dopant type is p-type, and thedopant concentration is formed of a Mg or Zn p-dopant. In an embodiment,the dopant concentration does not extend to a surface (e.g. top surface)of the first (e.g. top) cladding layer opposite the active layer. Thelight emitting structure may include a p-n junction on the sidewalls ofthe first (e.g. top) cladding layer. In an embodiment, the firstcladding layer includes alternating n-regions and n+ regions on top ofone another. For example, the n− regions may have an n-dopantconcentration less than the p-dopant concentration in the portion of thedopant concentration overlapping the n− regions. The n+ regions may havean n-dopant concentration greater than the p-dopant concentration in theportion of the dopant concentration overlapping the n+ regions.

In an embodiment, a light emitting structure (e.g. LED structure)includes a body (e.g. an LED body), which includes a first (e.g. top)cladding layer doped with a first dopant type, a contact layer (e.g.bottom contact layer) doped with a second dopant type opposite the firstdopant type, and an active layer between the first cladding layer andthe contact layer. The body may additionally include a second (e.g.bottom) cladding layer between the contact layer and the active layer,the second cladding layer doped with the second dopant type, a first(e.g. top) barrier layer between the first cladding layer and the activelayer, and a second (e.g. bottom) barrier layer between the secondcladding layer and the active layer. In an embodiment, lateral edges ofthe first (e.g. top) cladding layer and the second (e.g. bottom)cladding layer are closer to a center vertical axis of the body thanlateral edges of the first (e.g. top) barrier layer, the active layer,and the second (e.g. bottom) barrier layer. In an embodiment, the firstdopant type is n-type, the second dopant type is p-type. The lightemitting structure may further include a confinement region including ap-dopant concentration spanning the lateral edges of the n-doped first(e.g. top) cladding layer, the first (e.g. top) barrier layer, theactive layer, the second (e.g. bottom) barrier layer, the p-doped second(e.g. bottom) cladding layer, and the p-doped contact layer. In anembodiment, the p-dopant concentration occupies a larger volume of theactive layer than the first (e.g. top) barrier layer, and the p-dopantconcentration occupies a larger volume of the active layer than thesecond (e.g. bottom) barrier layer.

In an embodiment, a light emitting structure (e.g. LED structure)includes a body (e.g. an LED body), which includes a first (e.g. top)cladding layer doped with a first dopant type, a contact layer (e.g.bottom contact layer) doped with a second dopant type opposite the firstdopant type, an active layer between the first cladding layer and thecontact layer, a second (e.g. bottom) cladding layer between the contactlayer and the active layer, the second cladding layer doped with thesecond dopant type, and a barrier layer (e.g. top barrier layer) betweenthe first cladding layer and the active layer. In an embodiment, lateraledges of the first (e.g. top) cladding layer and the second (e.g.bottom) cladding layer are closer to a center vertical axis of the bodythan lateral edges of the barrier layer (e.g. top barrier layer) and theactive layer. In an embodiment, the first dopant type is n-type, thesecond dopant type is p-type. The light emitting structure may furtherinclude a regrown layer directly on the lateral edges of the first (e.g.top) cladding layer, the barrier layer, the active layer, the second(e.g. bottom) cladding layer, and the contact layer. The regrown layermay be doped with a dopant such as Te or Fe. In an embodiment, theregrown layer fills a volume directly between the contact layer (e.g.bottom contact layer) and the active layer, and laterally adjacent tothe second (e.g. bottom) cladding layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross-sectional side view illustration of a bulkLED substrate in accordance with an embodiment.

FIG. 1B is a schematic cross-sectional side view illustration of amultiple quantum well (MQW) active layer in accordance with anembodiment.

FIG. 2 is a flow chart illustrating a method of forming an LED includinga pillar structure and surface doping in accordance with an embodiment.

FIG. 3 is a schematic cross-sectional side view illustration of an arrayof mesa trenches and mesa structures formed in the device layer inaccordance with an embodiment.

FIG. 4 is a schematic cross-sectional side view illustration of an arrayof pillar structures formed on an array of mesa structures in accordancewith an embodiment.

FIG. 5A is a schematic cross-sectional side view illustration of ashallow surface doping profile in accordance with an embodiment.

FIG. 5B is a schematic cross-sectional side view illustration of deepsurface doping profile in accordance with an embodiment.

FIG. 5C is a schematic cross-sectional side view illustration of anarray of trenches and top bases formed in the device layer in accordancewith an embodiment.

FIG. 6 is a schematic cross-sectional side view illustration of apatterned passivation layer formed over an array of pillar structuresand mesa structures in accordance with an embodiment.

FIG. 7 is a schematic cross-sectional side view illustration of an arrayof bottom conductive contacts formed within the openings in thepatterned passivation layer in accordance with an embodiment.

FIG. 8 is a schematic cross-sectional side view illustration of apatterned sacrificial release layer formed over the array of pillarstructures and mesa structures in accordance with an embodiment.

FIG. 9 is a schematic cross-sectional side view illustration of apatterned bulk LED substrate bonded to a carrier substrate with astabilization layer in accordance with an embodiment.

FIG. 10 is a schematic cross-sectional side view illustration of anarray of LEDs including a top base, body, and pillar structure supportedby an array of stabilization posts in accordance with an embodiment.

FIG. 11 is a schematic cross-sectional side view illustration of anarray of LEDs including a body and pillar structure supported by anarray of stabilization posts in accordance with an embodiment.

FIGS. 12A-12B are schematic cross-sectional side view illustrations ofLEDs with a top base, body, pillar structure and a confinement regionwith a deep surface doping profile in accordance with embodiments.

FIGS. 13A-13B are schematic cross-sectional side view illustrations ofLEDs with a top base, body, pillar structure and a confinement regionwith a shallow surface doping profile in accordance with embodiments.

FIG. 14 is a schematic cross-sectional side view illustration of an LEDwith a body, pillar structure and a confinement region with a deepsurface doping profile in accordance with an embodiment.

FIG. 15 is a schematic cross-sectional side view illustration of an LEDwith a body, pillar structure and a confinement region with a shallowsurface doping profile in accordance with an embodiment.

FIG. 16 is a flow chart illustrating a method of forming an LEDincluding wafer level doping in accordance with an embodiment.

FIG. 17 is a schematic cross-sectional side view illustration of a bulkLED substrate in accordance with an embodiment.

FIG. 18 is a schematic cross-sectional side view illustration of a bulkLED substrate including a cladding layer with modulated doping inaccordance with an embodiment.

FIGS. 19A-19B are schematic cross-sectional side view illustrations ofdopant wells formed in bulk LED substrates in accordance withembodiments.

FIG. 19C is a close up schematic cross-sectional side view illustrationof an n-p superlattice where a dopant well overlaps a cladding layerwith modulated doping in accordance with an embodiment.

FIGS. 20A-20B are schematic cross-sectional side view illustrations ofan array of mesa trenches and mesa structures formed in a device layerin accordance with embodiments.

FIGS. 21A-21B are schematic cross-sectional side view illustrations ofLEDs including doped sidewalls in accordance with embodiments.

FIGS. 22A-22B are schematic cross-sectional side view illustrations ofLEDs including n-p superlattices along the LED sidewalls in accordancewith embodiments.

FIG. 23 is a flow chart illustrating a method of forming an LEDincluding selective etching of the cladding layers and shallow doping inaccordance with an embodiment.

FIG. 24 is a schematic cross-sectional side view illustration of anarray of mesa trenches and mesa structures formed in a device layer inaccordance with an embodiment.

FIG. 25 is a schematic cross-sectional side view illustration ofselectively etched cladding layers in accordance with an embodiment.

FIG. 26 is a schematic cross-sectional side view illustration of ashallow doping profile in accordance with an embodiment.

FIGS. 27A-27D are schematic cross-sectional side view illustrations ofLEDs including selectively etched cladding layers and shallow doping inaccordance with embodiments.

FIG. 28 is a flow chart illustrating a method of forming an LEDincluding selective etching of the cladding layers and regrowth inaccordance with an embodiment.

FIG. 29 is a schematic cross-sectional side view illustration of anarray of mesa trenches and mesa structures formed in a device layer inaccordance with an embodiment.

FIG. 30 is a schematic cross-sectional side view illustration ofselectively etched cladding layers in accordance with an embodiment.

FIG. 31 is a schematic cross-sectional side view illustration of aregrowth layer in accordance with an embodiment.

FIGS. 32A-32B are schematic cross-sectional side view illustrations ofan LED including selectively etched cladding layers and a regrowth layerin accordance with embodiments.

FIGS. 33A-33D are schematic cross-sectional side view illustrations of amethod of forming LEDs with a selectively etched active region inaccordance with an embodiment.

FIGS. 34A-34C are schematic cross-sectional side view illustrations of amethod of forming LEDs with a selectively etched sacrificial region inaccordance with an embodiment.

FIGS. 35A-35C are schematic cross-sectional side view illustrations of amethod of forming LEDs with a selectively etched sacrificial region inaccordance with an embodiment.

FIGS. 36A-36C are schematic cross-sectional side view illustrations of amethod of forming LEDs with selectively etched sacrificial regions inaccordance with an embodiment.

FIGS. 37A-37E are schematic cross-sectional side view illustrations of amethod of forming LEDs including forming an array of mesa trenches andmesa structures in accordance with embodiments.

FIG. 38 is a schematic cross-sectional side view illustration of an LEDintegrated on a backplane in accordance with an embodiment.

FIG. 39 is a schematic illustration of a display system in accordancewith an embodiment.

DETAILED DESCRIPTION

Embodiments describe LEDs and methods of forming LEDs with variousstructural configurations to mitigate non-radiative recombination at theLED sidewalls. In particular, embodiments describe micro LEDs andmethods of forming micro LEDs with various structural configurations tomitigate non-radiative recombination at the LED sidewalls. In accordancewith embodiments, the micro LEDs may be formed of inorganicsemiconductor-based materials, and have maximum lateral dimensionsbetween sidewalls of 1 to 300 μm, 1 to 100 μm, 1 to 20 μm, or morespecifically 1 to 10 μm, such as 5 μm where the LED lateral dimensionsapproach the carrier diffusion length.

It has been observed that the sidewalls for emissive LEDs, andparticularly for micro LEDs, may represent non-radiative recombinationsinks for injected carriers. This may be due to the sidewalls beingcharacterized by unsatisfied bonds, chemical contamination, andstructural damage (particularly if dry-etched). Injected carriersrecombine non-radiatively at states associated with these defects. Thus,the perimeter of an LED may be optically dead, and the overallefficiency of the LED is reduced. This non-radiative recombination canalso be a result of band bending at the surface leading to a density ofstates were electrons and holes can be confined until they combinenon-radiatively. The characteristic distance over which the sidewallsurface effect occurs is related to the carrier diffusion length, whichmay typically be 1-10 μm in some applications in accordance withembodiments. Thus, the efficiency degradation is particularly severe inmicro LEDs in which the LED lateral dimensions approach the carrierdiffusion length.

Such non-radiative recombination may have a significant effect on LEDdevice efficiency, particularly when the LED is driven at low currentdensities in the pre-droop region of its characteristic internal quantumefficiency (IQE) curve where the current is unable to saturate thedefects. In accordance with embodiments, sidewall surface modification,current confinement structures, and combinations thereof are describedsuch that the amount of non-radiative recombination near the exterior orside surfaces of the active layer can be reduced and efficiency of theLED device increased.

In one aspect, embodiments describe an LED structure that includes adoped confinement region (e.g. p-doped) including a dopant (e.g. Mg, Zn)concentration spanning sidewalls of an LED body and the bottom surfaceof the bottom barrier layer from which a pillar structure including adoped cladding layer (e.g. p-doped) protrudes. Thus, the embodimentsdescribe LED configurations that combine LED body sidewall surfacemodification to mitigate carrier diffusion to the LED surfaces withpillar structures for internally confining the current injection region.This may potentially 1) reduce carrier diffusion to the sidewallsurfaces, 2) screen Fermi-level pinning effect, and/or 3) reduce carrierdrift to the LED sidewall surfaces.

In another aspect, embodiments describe an LED structure thatincorporates a modulated doping profile (e.g. n+, n−) within a doped(e.g. n-type) cladding layer. In an embodiment, a dopant of the oppositedopant type (e.g. p-dopant such as Zn) is diffused into sidewalls of theLED structure. An n-p superlattice is formed where the p-dopant overlapsthe modulated n-type doping profile within the n-type cladding layer.Through proper adjustment of the resultant n- and p-layer thicknesses inthe n-p superlattice, the as-grown n-type doping profile, and theconcentration of the diffused p-dopant, an extended current-blockingstructure may be formed along the LED sidewalls. The back-to-back p-njunctions (i.e. extended depletion region) in the n-p superlattice maybe employed to 1) achieve some current confinement, 2) minimize leakagecurrent associated with a parasitic p-n junction formed by the p-dopantdiffusion, 3) minimize nonradiative recombination at the LED sidewalls,and/or 4) relax the alignment tolerance for the n-contact electrode.

In another aspect, embodiments describe LED structures that includeselectively etched cladding layers. In one embodiment, selectivelyetched cladding layers create entry points for shallow dopant (e.g.p-dopant such as Zn) diffusion into the active layer. In such anembodiment, the selective etching may allow for shallow p-dopantdiffusion with a lower thermal or time budget. In one embodiment, aregrown layer is formed after selective etching of the cladding layersin order to reduce surface recombination due to exposed surfaces nearthe active layer.

In another aspect, embodiments describe LED structures that include aselectively etched active region or sacrificial layer within the LEDbody. Selective etching may remove damage caused by during mesa trenchetching and/or confine current internally within the LED body. In anembodiment, selective etching is performed with a photo electro chemical(PEC) etching technique.

In various embodiments, description is made with reference to figures.However, certain embodiments may be practiced without one or more ofthese specific details, or in combination with other known methods andconfigurations. In the following description, numerous specific detailsare set forth, such as specific configurations, dimensions andprocesses, etc., in order to provide a thorough understanding of theembodiments. In other instances, well-known semiconductor processes andmanufacturing techniques have not been described in particular detail inorder to not unnecessarily obscure the embodiments. Reference throughoutthis specification to “one embodiment” means that a particular feature,structure, configuration, or characteristic described in connection withthe embodiment is included in at least one embodiment. Thus, theappearances of the phrase “in one embodiment” in various placesthroughout this specification are not necessarily referring to the sameembodiment. Furthermore, the particular features, structures,configurations, or characteristics may be combined in any suitablemanner in one or more embodiments.

The terms “top”, “bottom”, “above”, “over”, “to”, “between”, “spanning”,and “on” as used herein may refer to a relative position of one layerwith respect to other layers. One layer “above”, “over”, “spanning”, or“on” another layer or bonded “to” or in “contact” with another layer maybe directly in contact with the other layer or may have one or moreintervening layers. One layer “between” layers may be directly incontact with the layers or may have one or more intervening layers.Furthermore, the designation of “top” and “bottom” layers and surfacesrefers to the relative position of the layers with respect to oneanother, though the designations may be reversed, for example in anintegrated structure.

In the following description exemplary processing sequences andstructures are described for forming LEDs. Referring now to FIG. 1A, across-sectional side view illustration is provided of a bulk LEDsubstrate 100 in accordance with an embodiment of the invention. Thebulk LED substrate 100 structure may be applicable to a variety ofcompositions and designed emission spectra. For example, the bulk LEDsubstrate 100 may include II-VI materials, III-V nitride materials, orIII-V phosphide materials and designed for emission of a variety ofemission spectra. For example, the bulk LED substrate 100 may befabricated with an AlInGaP material system or ZnMgBeSSe material system.In a specific embodiment, the bulk LED substrate 100 is based on anAlInGaP material system and is designed for red color emission. Forexample, bulk LED substrate 100 may be designed for a peak emissionwavelength between 600 nm-750 nm, such as 625 nm. Thus, while thefollowing structures are described with regard to an AlInGaP materialsystem, the exemplary structures may be used for LEDs based on differentmaterial systems.

In one embodiment, formation of the bulk LED substrate 100 begins withthe formation of a device layer 117 on a growth substrate 101, such as aGaAs growth substrate, for example with a thickness of 250-1,000 μm.Growth substrate 101 may optionally be doped, for example with an n-typedopant such as silicon (Si) or tellurium (Te). Layers 102-114 of thedevice layer 117 may then be grown on the growth substrate 101 using asuitable technique such as metal organic chemical vapor deposition(MOCVD). As shown, an n-type contact layer 102 is optionally grown onthe growth substrate 101, for example to a thickness of 0.1-1.0 μm. Inan embodiment, n-type contact layer 102 is formed of AlInGaP with a Sior Te dopant concentration of 0.5-4×10¹⁸ cm⁻³. The n-type contact layer102 may not be present for all LED applications. An n-type claddinglayer 104 is then grown on the optional n-type contact layer 102, forexample to a thickness of 0.05-0.5 μm. N-type cladding layer 104 may beformed of materials such as AlInP, AlGaInP, and AlGaAs. In anembodiment, n-type cladding layer 104 is formed of AlInP with a Sidopant concentration of 1×10¹⁸ cm⁻³. An n-side (top) barrier layer 106is then grown on the n-type cladding layer 104, for example to athickness of 0.05-0.5 μm. N-side barrier layer 106 may be formed ofmaterials such as AlInP, AlGaInP, and AlGaAs. In an embodiment, n-sidebarrier layer 106 is formed of AlInGaP, and is unintentionally dopedduring growth. In an embodiment, the n-side barrier layer 106 does nothave a graded composition (e.g. Aluminum content is uniform). An activeregion 108 is then grown on the n-side barrier layer 106. Active region108 may include one or more quantum well (QW) layers or bulk activelayers. In an embodiment illustrated in FIG. 1B, the one or more quantumwell layers 108A or bulk active layers are formed of InGaP or AlInGaP,separated by spacer layers 108B of the same alloy (e.g. AlInGaP) as thesurrounding barrier layers. A p-side (bottom) barrier layer 110 is thenoptionally grown on the active layer 108, for example to a thickness of0.05-0.5 μm, or more specifically approximately 100 nm. P-side barrierlayer 110 may be formed of materials such as AlInP, AlGaInP, and AlGaAs.In an embodiment, p-side barrier layer 110 is formed of AlInGaP, and isunintentionally doped during growth. A p-type (bottom) cladding layer112 may then be formed on the p-side barrier layer 110. The p-typecladding layer 112 may be formed of materials such as AlInP, AlGaInP,and AlGaAs. In an embodiment, p-type cladding layer 112 is formed ofAlInP with a Mg dopant concentration of 5×10¹⁷ cm⁻³-1.5×10¹⁸ cm⁻³. In anembodiment, the p-type cladding layer 112 may have a substantiallyuniform p-dopant concentration, less a concentration gradient due todiffusion with the surrounding layers. In an embodiment, the p-dopantconcentration is not uniform. For example, doping may begin after aspecific set back distance, such as 100-200 nm into the p-type claddinglayer 112. A p-type contact layer 114 is then optionally grown on thep-type cladding layer 112, for example to a thickness of 0.1-50.0 μm,for example to 0.1-1.5 μm for a thinner LED. In an embodiment, theoptional p-type contact layer 114 is formed of GaP or GaAs, for example,with a Mg, Zn, or C dopant concentration of 1×10¹⁸ 1×10¹⁹ cm⁻³.

In accordance with embodiments, the barrier layers 106, 110 may beformed of a material with a large conduction band offset with respect tothe one or more quantum well layers in the active layer 108. In thisaspect, a maximum conduction band offset to the quantum wells confineselectrons to the quantum wells. In accordance with embodiments, thedoped cladding layers 104, 112 may be selected to have a high band gapin order to confine the injected carriers. For example, the dopedcladding layers 104, 112 may have a higher bandgap energy than theadjacent barrier layers. In an embodiment, the barrier layers 106, 110are (Al_(x)Ga_(1-x))_(0.5)In_(0.5)P alloys with 0.2≤x≤0.8, such as0.5≤x≤0.8. In an embodiment, the doped cladding layers 104, 112 are(Al_(x)Ga_(1-x))_(0.5)In_(0.5)P alloys with 0.6≤x≤1.0.

Referring now to FIG. 2 a flow chart is provided of a method of formingan LED including a pillar structure and surface doping in accordancewith an embodiment. In interest of clarity, the following description ofFIG. 2 is made with regard to reference features found in other figuresdescribed herein. At operation 2010 an array of mesa structures 130 isformed in the device layer 117 of a bulk LED substrate 100. An array ofpillar structures 140 is formed on the array of mesa structures 130 atoperation 2020. At operation 2030 dopants are implanted or diffused intoexposed surfaces of the array of mesa structures 130 and the devicelayer laterally between adjacent mesa structures to form confinementregions 150. In some embodiments, a mask used during etching of thepillar structures 140 may be subsequently used during implantation ordiffusion at operation 2030. In accordance with embodiments, the orderof operations 2010 and 2020 can be reversed.

In accordance with embodiments, locations of the dopant concentrationprofiles of confinement regions 150 are described as encroaching fromthe LED sidewalls or encroaching laterally above sidewalls of a pillarstructure. Top conductive contacts are also described as being directlyover the dopant concentration profiles of the confinement regions. It isto be appreciated that dopant concentration profiles due to implantationor diffusion could potentially cover a wide range of dopant profiles,that range from those that affect operation of the LED to those withnegligible effect. Accordingly, in accordance embodiments the edges ofthe confinement regions 150 may be characterized by a threshold amountof dopant concentration, such as one that approaches or exceeds thenominal in-situ dopant concentration of the relative cladding layers104, 112 or the n− dopant concentration in a modulated cladding layer.In an exemplary embodiment, a dopant concentration of 1×10¹⁷ cm⁻³ mayapproach the in-situ dopant concentration of the relative claddinglayers 104, 112. In an exemplary embodiment, a dopant concentrationgreater than 1×10¹⁸ cm⁻³ may exceed the in-situ dopant concentration ofthe relative cladding layers 104, 112. In an exemplary embodiment, adopant concentration greater than 5×10¹⁷ cm⁻³ may exceed the in-situ n−dopant concentration in a modulated cladding layer.

FIG. 3 is a schematic cross-sectional side view illustration of an arrayof mesa trenches 120 and mesa structures 130 formed in the device layerin accordance with an embodiment. In the particular embodimentillustrated contact layer 114, 102 are not separately illustrated.However, contact layers 114, 102 may be present similarly as describedwith regard to FIG. 1A. In the following description of FIGS. 3-15,processing of cladding layer 112 may include similar processing ofcontact layer 114 (not illustrated separately), and processing ofcladding layer 104 may include similar processing of contact layer 102(not separately illustrated). Accordingly, processing of cladding layer112 may represent processing of doped (e.g. p-doped) cladding layer 112and doped (e.g. p-doped) contact layer 114. Similarly, processing ofcladding layer 104 may represent processing of doped (e.g. n-doped)cladding layer 104 and doped (e.g. n-doped) contact layer 102. In theparticular embodiment illustrated in FIG. 3, mesa trenches 120 areformed at least partially through cladding layer 104. In an embodiment,mesa trenches 120 may be formed through cladding layer 104 and into (orstop on) contact layer 102. Alternatively, trenches may be formedcompletely through contact layer 102. As will become more apparent inthe following description the width and depth of the mesa trenches 120at least partially determines the dimensions of the LED bodies 132 (seeFIGS. 12A-15) that will be formed.

Etching may be formed using a suitable technique such as wet etching ordry etching techniques. In an embodiment, mesa trenches 120 are formedby a first partial dry etch, then the wafer is transferred to an MOCVDchamber to complete etching of the mesa trenches 120. In this manner,the final etched surfaces are conditioned by etching in the MOCVDchamber and physical damage created during the dry etching operation isremoved by the chemical etching in the MOCVD chamber. Exemplary dryetching techniques that may be used include reactive ion etching (RIE),electro-cyclotron resonance (ECR), inductively coupled plasma reactiveion etching (ICP-RIE), and chemically assisted ion-beam etching (CAIBE).The dry etching chemistries may be halogen based, containing speciessuch as Cl₂, BCl₃, or SiCl₄. The etching chemistries within the MOCVDchamber may additionally be at an elevated temperature, such as 400°C.-700° C. The specific etching chemistry may include a combination of acorrosive etchant and a group V decomposition suppressant to stabilizethe group V element, and suppress decomposition that may otherwise occurat the elevated etching temperature. In an embodiment, the etchingchemistry includes a corrosive etchant such as HCl or Cl₂, and a group Vdecomposition suppressant such as PH₃. In an embodiment, the etchingchemistry includes a corrosive etchant such as HCl, Cl₂, or H₂ (orcombinations thereof), and a group V decomposition suppressant such asNH₃.

In an embodiment, an array of pillar structures 140 are formed on thearray of mesa structures 130, as illustrated in FIG. 4. The width of thepillar structures 140 may at least partially determine the ability toincrease current density within the LED device as well as the ability toconfine current internally within the LED device and away from theexternal sidewalls where non-radiative recombination may occur. In someembodiments, pillar structures 140 have a width or diameter of 1-10 μm,such as 2.5 μm. Pillar structures 140 may be formed using similaretching techniques used for mesa trenches 120. In an embodiment, masklayers 142 are used to pattern the pillar structures 140. Mask layers142 may be formed with a dielectric material, such as SiO₂ that cansurvive the high temperatures and aggressive etch chemistries.

Referring now to FIGS. 5A-5B dopants are implanted or diffused intoexposed surfaces of the array of mesa structures 130 and the devicelayer laterally between adjacent mesa structures to form confinementregions 150. In the embodiment illustrated in FIG. 5A, the confinementregions 150 have a shallow surface doping profile in which the verticaldepth of the doping profile that extends from the top surface of themesa structure 130 (which will become LED body 132 bottom surface 133)and stops before reaching the active layer 108. Thus, the shallow dopingprofile may stop within the barrier layer 110. In an embodiment, thebarrier layer 110 is an unintentionally doped layer, less the dopingfrom the confinement region 150. In the embodiment illustrated in FIG.5B, the confinement regions 150 have a deep surface doping profile inwhich the vertical depth of the doping profile extends from the topsurface of the mesa structure 130 (which will become LED body 132 bottomsurface 133) and through the active region layer 108. In an embodiment,the vertical depth of the doping profile stops within the barrier layer106. In an embodiment, the barrier layers 110, 106 are unintentionallydoped layers, less the doping from the confinement region 150. In aspecific embodiment, the confinement region 150 dopant is Zn (p-dopant).

In accordance with embodiments, the doping of confinement regions 150may be n-type or p-type. In an embodiment, an element that produces ahigh doping concentration and low mobility is utilized. For example,this may be obtained if the acceptor or donor localization is relativelylarge (e.g. in order of 100 meV). In accordance with embodiments, lowmobility of the confinement regions 150 due to relatively deep acceptorlevel inhibits strong current leakage. As a result, only minoritycarriers (e.g. electrons) may reach the LED surfaces, and hence thenon-radiative surface recombination may be reduced. The p-doping nearthe LED surfaces may additionally screen away Fermi-level pinning if thep-dopant concentration is greater than 1×10¹⁸ cm⁻³.

Referring now to FIG. 5C in an embodiment an array of trenches and topbases 160 are formed in the device layer. In the particular embodimentillustrated in FIG. 5C, the trenches 166 may extend past the dopingprofile (shallow or deep) of the confinement region 150. For example, asillustrated in FIGS. 12B and 13B, this may aid in the formation of apassivation layer 170 along sidewalls 161 of the top base 160 of theLED.

FIG. 6 is a schematic cross-sectional side view illustration of apatterned passivation layer 170 is optionally formed over an array ofpillar structures 140 and mesa structures 130 in accordance with anembodiment. The patterned passivation layer 170 in FIG. 6 is formed overthe patterned LED substrate illustrated in FIG. 5B, however, embodimentsare not so limited and a patterned passivation layer 170 can be formedover a variety of structures including those illustrated in FIG. 5A andFIG. 5C. In interests of clarity, and to not obscure embodiments,separate processing sequences are not illustrated forming a patternedpassivation layer 170 on the structures illustrated in FIG. 5A or 5C.

In an embodiment, passivation layer 170 is formed of an electricallyinsulating material such as an oxide or nitride. In an embodiment,passivation layer 170 is approximately 50 angstroms to 3,000 angstromsthick Al₂O₃, and may be formed using a high quality thin film depositionprocess such as atomic layer deposition (ALD). As will become apparentin the following description a high quality thin film may protect theintegrity of the passivation layer 170 during the sacrificial releaselayer etch operation. Openings 172 may be formed over the pillarstructures 140 to expose the (bottom) surface 143 of the pillarstructures 140, such as the (bottom) surface of the contact layer 114 orcladding layer 112.

Referring now to FIG. 7, an array of bottom conductive contacts 180 areformed on the bottom surfaces 143 of the array of pillar structures 140.Where the optional sidewall passivation layer 170 is present, the bottomconductive contacts 180 may be formed on the bottom surfaces 143 of thepillar structures and within the openings 172. The optional passivationlayer 170 may additionally prevent shorting between the conductivecontacts 180 and other areas of the LED, such as the mesa structures130, which will become the LED bodies 132. Bottom conductive contacts180 may include multiple layer stacks. Exemplary layers can include anelectrode layer (e.g. to make ohmic contact with contact layer 114),mirror layer (e.g. nickel or silver), adhesion/barrier layer (e.g.titanium), diffusion barrier (e.g. platinum), and a bonding layer (suchas gold) for bonding the completed LEDs to a receiving substrate.

Following the formation of the bottom conductive contacts 180, asacrificial release layer 190 may be formed over the patterned devicelayer as illustrated in FIG. 8. The sacrificial release layer 190 may bepatterned to form openings 192 over the bottom conductive contacts 180.The sacrificial release layer 190 may be formed of an oxide (e.g. SiO₂)or nitride (e.g. SiN_(x)), though other materials may be used which canbe selectively removed with respect to the other layers. The height,width, and length of the openings 192 will correspond to the height,length, and width of the stabilization posts to be formed, andresultantly the adhesion strength that must be overcome to pick up thearray of LEDs (e.g. micro LEDs) that are poised for pick up on the arrayof stabilization posts.

Referring now to FIG. 9, the patterned structure on the growth substrate101 is bonded to a carrier substrate 220 with an adhesive bondingmaterial to form stabilization layer 210. In an embodiment, the adhesivebonding material is a thermosetting material such as benzocyclobutene(BCB) or epoxy. The portion of the stabilization material that fillsopenings 192 corresponds to the stabilization posts 212 of thestabilization layer 210, and the portion of the stabilization materialthat fills the mesa trenches (and optionally base trenches) becomes thestabilization cavity sidewalls 214 of the stabilization layer 210.

After bonding to the carrier substrate 220, the growth substrate 101 maybe removed utilizing a suitable technique such as laser lift-off,etching, or grinding to expose the device layer 117. Any remainingportions of the (n-doped) cladding layer 104 or (n-doped) contact layer102 connecting the separate mesa structures 130 may then be removedusing etching or grinding to form laterally separate p-n diodes. In theembodiment illustrated in FIG. 10, trenches 194 are etched through thedevice layer 117 to expose the sacrificial release layer 190. Formationof trenches 194 may result in the formation of top base 160, if notalready formed. In the embodiment illustrated in FIG. 11, a thickness ofthe device layer 117 (e.g. contact layer 102 and/or cladding layer 104)is uniformly reduced to expose the sacrificial release layer 190. In theembodiment illustrated in FIG. 11, the thickness reduction may result inan LED without a top base 160. In an alternative embodiment in whichtrenches 166 were previously formed (e.g. FIG. 5C), the uniformthickness reduction may result in an LED with a top base 160.

A top conductive contact 182 may be formed over each laterally separatep-n diode resulting in LEDs 195, supported by stabilization posts 212and embedded in a sacrificial release layer 190. Once ready for transferto a receiving substrate, the sacrificial release layer 190 may beselectively removed, for example, with a vapor HF release operation. TheLEDs 195 may then be poised for pick up and transfer to a receivingsubstrate, for example, with an electrostatic transfer head assemblyincluding an array of electrostatic transfer heads.

FIGS. 12A-15 represent various LED structures that may be obtained inaccordance with embodiments, including possible combinations ofconfinement region 150 dopant profiles, passivation layers 170, andpresence of a top base 160 structure. In the embodiments illustrated,each of the LED 195 configurations include a pillar structure 140, and adoped current confinement region 150 along sidewalls of the LED. Morespecifically, each embodiment illustrated in FIGS. 12A-15 includes anLED body 132 that includes a top cladding layer 104 doped with a firstdopant type (e.g. n-type), an active layer 108 below the top claddinglayer 104, and a bottom barrier layer 110 below the active layer 108. Apillar structure 140 protrudes from a bottom surface 133 of the LED body132, such as a bottom surface of the bottom barrier layer 110. Thepillar structure 140 includes a bottom cladding layer 112 doped with asecond dopant type (e.g. p-type) opposite of the first dopant type (e.g.n-type). Alternatively, the dopant types may be reversed. A confinementregion 150 including a dopant concentration spans sidewalls 135 of theLED body 132 and the bottom surface 133 of the LED body 132 (e.g. bottomsurface of the bottom barrier layer 110). In accordance withembodiments, the dopant concentration of the confinement region 150 isformed of the second dopant type (e.g. p-type, such as Mg, Zn) andencroaches from the LED body sidewalls 135 toward a center vertical axis199 of the LED 195 and from the bottom surface 133 of the LED body 132(e.g. bottom surface of the bottom barrier layer 110) toward the activelayer 108. As illustrated, the dopant concentration also encroacheslaterally (and directly) above sidewalls 141 of the pillar structure 140within the bottom barrier layer 110 toward the center vertical axis 199of the LED 195.

In each of the embodiments illustrated the confinement region 150 dopantconcentration encroaches further toward the center vertical axis 199 ofthe LED 195 within the bottom barrier layer 110 than within the activelayer 108 and the top cladding layer 104. For example, the confinementregion 150 dopant concentration may be characterized as a Z-shape (e.g.FIGS. 12A-12B, 13A-13B) or L-shape (e.g. FIGS. 14-15). A Z-shape mayinclude the L-shape.

A conformal passivation layer 170 may optionally be formed on andspanning the sidewalls 135 of the LED body 132, the sidewalls 141 of thepillar structure 140, and a bottom surface 143 of the pillar structure140. An opening 172 may be formed in the conformal passivation layer 170on the bottom surface 143 of the pillar structure, and a bottomconductive contact 180 formed on the bottom surface 143 of the pillarstructure 140 and within the opening 172 of the conformal passivationlayer 170.

Referring now to FIGS. 12A-12B and FIGS. 13A-13B in some embodiments,the LED 195 includes a top base 160, and the LED body 132 protrudes froma bottom surface 163 of the top base 160. As shown, the bottom surface163 of the top base 160 is wider than the LED body 132, similarly as thebottom surface 133 of the LED body 132 is wider than the pillarstructure 140 that protrudes from the bottom surface 133. In anembodiment, the confinement region 150 dopant concentration spans thebottom surface 163 of the top base, and encroaches toward a top surface165 of the top base 160. The confinement region 150 dopant concentrationmay not encroach all the way to the top surface 165 of the top base 160.A top conductive contact 182 may be formed on the top surface 165 of thetop base 160, and a bottom conductive contact 180 may be formed on thebottom surface 143 of the pillar structure 140.

Referring to FIGS. 12A-12B, as described above with regard to FIG. 5B,the confinement region 150 dopant concentration may have a deep surfacedoping profile in which the vertical depth of the doping profile extendsfrom the bottom surface 133 of the LED body 132 through the activeregion layer 108. In an embodiment, the vertical depth of the dopingprofile stops within the barrier layer 106. In an embodiment, theconfinement region 150 dopant concentration encroaches further towardthe center vertical axis 199 of the LED 195 within the bottom barrierlayer 110 and the active layer 108 than within the top cladding layer104. In an embodiment, the barrier layers 110, 106 are unintentionallydoped layers, less the doping from the confinement region 150. In aspecific embodiment, the confinement region 150 dopant is Zn (p-dopant).

Referring to FIGS. 13A-13B, as described above with regard to FIG. 5A,the confinement region 150 dopant concentration may have a shallowsurface doping profile in which the vertical depth of the doping profileextends from the bottom surface 133 of the LED body 132 and stops beforereaching the active layer 108. Thus, the shallow doping profile may stopwithin the barrier layer 110. In an embodiment, the confinement region150 dopant concentration encroaches further toward the center verticalaxis 199 of the LED 195 within the bottom barrier layer 110 than withinthe active layer 108 and the top cladding layer 104. In an embodiment,the barrier layer 110 is an unintentionally doped layer, less the dopingfrom the confinement region 150. In a specific embodiment, theconfinement region 150 dopant is Zn (p-dopant).

Referring now to the embodiments illustrated FIGS. 12A and 13A, aconformal sidewall passivation layer 170 is illustrated as spanningalong the bottom surface 143 of the pillar structure 140, sidewalls 135of the LED body 132, and the bottom surface 163 of the top base 160.Referring now to FIGS. 12B and 13B, the conformal sidewall passivationlayer 170 is additionally illustrated as also spanning the sidewalls 161of the top base 160. The different structural configurations may beattributed to when the top base 160 is formed. For example, the top base160 of FIGS. 12A and 13A may have been formed as described above withregard to FIG. 10, after the formation of the sidewall passivation layer170 and bonding to the carrier substrate 220. The top base 160 of FIGS.12B and 13B may have been formed as described above with regard to FIG.5C, prior to the formation of the sidewall passivation layer 170.

The formation of a top base 160 may allow for relaxed alignmenttolerances of the top conductive contacts 182. For example, in theembodiments illustrated in FIGS. 12A-12B and FIGS. 13A-13B, the area ofthe top surface 165 of the top base 160 is greater than the areas of theLED body 132 and pillar structure 140. Additionally, the confinementregion 150 doping profiles may not extend to the top surface 165 of thetop base 160. In an embodiment, were the top base 160 is n-doped, thepillar structure 140 is p-doped, and the confinement region 150 isp-doped, the vertical separation between the confinement region 150 andthe top conductive contact 182 may function to prevent a p-doped shuntpath along the LED sidewalls.

Referring now to FIGS. 14-15 embodiments are illustrated in which theLEDs 195 do not include a top base layer 160. In the embodimentillustrated in FIG. 14 the confinement region 150 dopant concentrationhas a deep surface doping profile as previously described. In theembodiment illustrate din FIG. 15 the confinement region 150 dopantconcentration has a shallow surface doping profile as previouslydescribed. In the particular embodiments illustrated in FIGS. 14-15, theconfinement region 150 dopant concentration may extend to the topsurface 137 of the LED body 132. In the embodiments illustrated, the topconductive contact 182 is not formed directly on the confinement region150.

In some embodiments, the doping profiles of the confinement regions areformed at the wafer level prior to the formation of mesa structures.FIG. 16 is a flow chart illustrating a method of forming an LEDincluding wafer level doping in accordance with an embodiment. Ininterest of clarity, the following description of FIG. 16 is made withregard to reference features found in other figures described herein. Atoperation 1610 an array of dopant wells 158 is formed in the devicelayer 117. Each dopant well 158 may optionally extend into a claddinglayer 104 with modulated doping. At operation 1620 an array of mesatrenches 120 is formed in the array of dopant wells 158 in the devicelayer to form an array of mesa structures 130 including confinementregions 150 along sidewalls 131 of the mesa structures 130. In anembodiment, the confinement regions 150 overlap the cladding layers 104with modulated doping to form n-p superlattices 159.

Referring now to FIG. 17 a schematic cross-sectional side viewillustration is provided of a bulk LED substrate 100 in accordance withan embodiment. The bulk LED substrate 100 illustrated in FIG. 17 may besubstantially similar to the bulk LED substrate illustrated anddescribed with regard to FIG. 1A. Contact layers 102, 114 are notseparately illustrated, though may be present similarly as describedabove. FIG. 18 is a schematic cross-sectional side view illustration ofa bulk LED substrate including a cladding layer 104 with modulateddoping in accordance with an embodiment. The bulk LED substrate 100illustrated in FIG. 18 may be substantially similar to the bulk LEDsubstrate illustrated and described with regard to FIG. 17, with onedifference being the cladding layer 104 with modulated doping. Contactlayers 102, 114 are not separately illustrated, though may be presentsimilarly as described above.

FIGS. 19A-19B are schematic cross-sectional side view illustrations ofdopant wells 158 formed in bulk LED substrates in accordance withembodiments. In the embodiment illustrated in FIG. 19A the dopant wells158 extend into and terminate in the cladding layer 104. In theembodiment illustrated in FIG. 19B the dopant wells 158 extend throughthe cladding layer 104. Dopant wells 158 may be formed using techniquessuch as implantation, solid source diffusion, or vapor diffusion. In anembodiment dopant wells 158 are p-type, and include a dopant profile ofa dopant such as a Zn or Mg. As will become apparent in the followingdescription, the dopant wells 158 may displace the p-n junction.

In the particular embodiments illustrated in FIGS. 19A-19B claddinglayer 104 includes modulated doping. In some embodiments, cladding layer104 is similar to cladding layer 104 described above with regard to FIG.17. Referring now to FIG. 19C a close up schematic cross-sectional sideview illustration is provided of an n-p superlattice 159 where a dopantwell 158 overlaps a cladding layer 104 with modulated doping inaccordance with an embodiment. In the particular embodiment illustrated,the cladding layer 104 includes modulated n-type doping between a highvalue (e.g. n+) and a low value (e.g. n−). In an embodiment the highvalue (e.g. n+) is chosen to be sufficiently high to remain n-type afterdiffusion of the dopant well 158 (e.g. Zn diffusion), so that the regionis not fully compensated by the Zn; while the low value (e.g. n−) ischosen to be converted to p-type by the dopant well 158 diffusion (e.g.Zn diffusion). For example, if the dopant well 158 includes a dopantconcentration (e.g. Zn) of about 1×10¹⁸ cm⁻³, the n+ regions may bedoped at a level above this, and with a significant margin to ensurereproducibility, such as greater than or equal to 2×10¹⁸ cm⁻³. Likewise,the n− regions may have a donor concentration less than the (Zn) dopantwell 158 concentration, such as 5×10¹⁷ cm⁻³. In an embodiment, at theseexemplary donor concentrations the Zn diffusion converts the n-regionsto p-type, while the n+ regions remain n-type, and an n-p superlattice159 is created.

FIGS. 20A-20B are schematic cross-sectional side view illustrations ofan array of mesa trenches 120 and mesa structures 130 formed in thedevice layer in accordance with embodiments. As shown the mesa trenches120 may be formed through the dopant wells, resulting in confinementregions 150 along sidewalls 131 of the mesa structures 130. Inaccordance with embodiments, the mesa structures 130 will become LEDbodies 132, and sidewalls 131 of the mesa structures will becomesidewalls 135 of the LED bodies 132. In the embodiment illustrated inFIG. 20A, the mesa trenches 120 may be formed vertically below thedopant wells, and resultant confinement regions 150. In the embodimentillustrated in FIG. 20B, the mesa trenches 120 may be formed completelythrough the cladding layer 104.

Following the formation of mesa structures 130, the patterned bulk LEDsubstrates of FIGS. 20A-20B may be processed similarly as illustratedand described above with regard to FIGS. 6-11 to form an array of LEDs195 that are poised for pick up and transfer to a receiving substrate.FIGS. 21A-21B are schematic cross-sectional side view illustrations ofLEDs 195 including doped sidewalls in accordance with embodiments. Inparticular the LEDs 195 illustrated in FIGS. 21A-21B may be formedutilizing the bulk LED substrate 100 illustrated in FIG. 17. FIGS.22A-22B are schematic cross-sectional side view illustrations of LEDs195 including n-p superlattices 159 along the LED sidewalls inaccordance with embodiments. In particular the LEDs 195 illustrated inFIGS. 22A-22B may be formed utilizing the bulk LED substrate 100illustrated in FIG. 18.

As illustrated, the LEDs 195 include an LED body 132 which includes atop cladding layer 104 doped with a first dopant type (e.g. n-type), anactive layer 108 below the top cladding layer 104, and a bottom claddinglayer 112 below the active layer 108. The bottom cladding layer 112 maybe doped with a second dopant type (e.g. p-type) opposite the firstdopant type. A confinement region 150 including a dopant concentration(e.g. p-dopant such as Mg or Zn) spans sidewalls 105 of the top claddinglayer 104, sidewalls 109 of the active layer 108, and sidewalls 113 ofthe bottom cladding layer 112, and the dopant concentration encroachesfrom the sidewalls 105, 109, 113 toward a center vertical axis 199 ofthe LED 195. In an embodiment, the confinement region 150 dopantconcentration does not extend to a top surface of the top cladding layer104. In the embodiment illustrated in FIG. 21A a p-n junction may existat the sidewalls 105 of the top cladding layer 104. In such aconfiguration, the alignment tolerance is relaxed for the top conductivecontact 182, which may be formed directly over the confinement region150. In the embodiment illustrated in FIG. 21B a p-n junction may existat the top surface 137 of the LED body 132. In such a configuration, theconfinement region 150 dopant concentration may extend to the topsurface 137 of the LED body 132. In the embodiment illustrated, the topconductive contact 182 is not formed directly on the confinement region150 in order to avoid the formation of a shunt path along sidewalls ofthe LED body 132.

In a conventional LED the p-n junction extends laterally across theactive layer to sidewalls of the active layer/LED. It has been observedthat mid-gap electronic states associated with unsatisfied bonds and/orcrystal damage at the surface may be responsible for non-radiativerecombination and diode leakage current. In accordance with embodiments,a confinement region 150 adjacent sidewalls of the LED suppressesnon-radiated recombination. In the embodiments illustrated in FIGS.21A-22B, the confinement region 150 dopant (e.g. Zn) concentrationconverts the n-type materials to p-type, and the active region p-njunction is displaced from the active layer. In the embodimentillustrated in FIG. 21A the p-n junction has been shifted into thecladding layer 104. In the embodiment illustrated in FIG. 21B the p-njunction has been shifted to the top surface 137 of the LED body 132.Mid-gap electronic states associated with unsatisfied bonds and/orcrystal damage at the LED sidewalls of the exposed p-n junction maystill be responsible for non-radiative surface recombination and diodeleakage at the exposed p-n junctions of FIGS. 21A-21B.

In the embodiments illustrated in FIGS. 22A-22B the top cladding layer104 includes modulated doping. For example, the top cladding layer 104may include alternating n-regions and n+ regions on top of one another.In an embodiment, the n− regions have an n-dopant concentration lessthan the p-dopant concentration in the portion of the confinement region150 overlapping the n− regions. In an embodiment, the n+ regions have ann-dopant concentration greater than the p-dopant concentration in theportion of the confinement region 150 overlapping the n+ regions.

Several conditions may apply in the n-p super lattice 159. 1) In oneembodiment, both the p-type and n-type layers are fully depleted of freecarriers by the back-to-back p-n junctions. In this case, the doping andthickness of each layer is insufficient to fully accommodate thedepletion from adjacent layers. The n-p superlattice 159 becomesdepleted of free carriers. 2) In one embodiment, one or both of thelayers in the n-p super lattice 159 is depleted, and the second type isnot. In this case, one of the layers is not sufficiently thick enough toaccommodate depletion from adjacent layers. For the second layer type,the thickness is sufficient to accommodate the depletion, so that freecarriers exist in the second layer type. 3) In one embodiment, bothlayers are not depleted, that is each is sufficiently thick toaccommodate the depletion. In this case, the n-p super lattice 159alternating n-p junctions serve to block current.

Accordingly, the modulated doping structure may modify the LED sidewallcarrier-concentration profile. The extended depletion region orback-to-back p-n junctions along the LED sidewall may be employed to 1)control the size of the electrically-injected region, i.e. achieve somecurrent confinement, 2) minimize leakage current associated with theparasitic exposed p-n junction formed by the confinement region 150, 3)minimize non-radiative recombination at the LED sidewalls, and 4) relaxthe alignment tolerance for the top conductive contact 182.

In the embodiment illustrated in FIG. 22A the confinement region 150dopant concentration does not extend to the top surface 137 of the LEDbody 132. In such a configuration, the alignment tolerance is relaxedfor the top conductive contact 182, which may be formed directly overthe confinement region 150. In the embodiment illustrated in FIG. 22Bthe confinement region 150 dopant concentration may optionally extend tothe top surface 137 of the LED body 132. In such an embodiment, the topconductive contact 182 may also be formed directly over the confinementregion 150, with the n-p superlattice inhibiting a shunt path along theLED sidewalls. In some embodiments, the top conductive contact 182 isnot formed directly over the confinement region 150.

Up until this point the bulk LED substrates 100 and LEDs have beendescribed with regard to, but not limited to, AlInGaP material systemsspecifically. In other embodiments, the bulk LED substrates and LEDs maycorrespond to blue emitting (e.g. 450-495 nm wavelength), green emitting(e.g. 495-570 nm wavelength) systems, or deep blue emitting systems, forexample. Referring now to FIGS. 37A-37E schematic cross-sectional sideview illustrations are provided of a method of forming LEDs includingforming an array of mesa trenches and mesa structures in accordance withembodiments.

FIG. 37A is a cross-sectional side view illustration of an simplifiedbulk LED substrate 400, in which more layers may be present than thoseillustrated. As illustrated, the bulk LED substrate 400 includes agrowth substrate 401, a doped semiconductor layer 404 (e.g. n-doped) anactive region 408 on the doped semiconductor layer 404, and a dopedsemiconductor layer 412 (e.g. p-doped) on the active region 408. By wayof example, in an embodiment, the bulk LED substrate 400 is designed foremission of blue or green light, and the materials are nitride based.The followed listing of materials for blue or green emission is intendedto be exemplary and not limiting. For example the layers forming thedoped semiconductor layers 404, 412 may include GaN, AlGaN, InGaN.Active region 408 may be formed of a variety of materials, such as butnot limited to InGaN. In such an embodiment, a suitable growth substrate401 may include, but is not limited to, silicon and sapphire.

In interests of clarity, in the following descriptions related to bulkLED substrates 400, reference to features similar to those describedwith regard to processing of the bulk LED substrates 100 will be madeusing like reference numbers, for example, with reference number 400corresponding substantially to reference number 100. Additionally, it isunderstood that the illustrated bulk LED substrates 400 are simplified.For example, doped semiconductor layer 404 may include multiple layers,such as a contact layer, cladding layer, and/or barrier layer.Similarly, doped semiconductor layer 412 may include multiple layers,such as a barrier layer, cladding layer, and contact layer.

Referring now to FIGS. 37B-37C, a bottom conductive contact 480 isformed over the doped semiconductor layer 412, followed by the formationof a mask layer 442, and the implantation of ions to form an array ofdopant wells 458. Exemplary ions include Al, Mg, and Si though otherselements may be suitable.

Following the formation of dopant wells 458, the mask layer 442 may beremoved as illustrated in FIG. 37D, and mesa trenches 420 formed throughthe dopant wells 458 as illustrated in FIG. 37E, forming confinementregions 450. In accordance with embodiments, the confinement regions 450may function as a current aperture to keep the current away from highdamage regions that may have been caused during etching (e.g. plasmaetching) of the mesa trenches 420. Following additional processing, theresulting LEDs may be similar to those illustrated and described withregard to FIGS. 21A-22B.

In an embodiment, the LED structure includes an LED body with a topdoped semiconductor layer 404 doped with a first dopant type (e.g.n-type), an active region 408 below the top doped semiconductor layer404, a bottom doped semiconductor layer 412 doped with a second dopanttype (e.g. p-type) opposite the first dopant type, and a confinementregion 450 including a dopant concentration spanning sidewalls of thetop doped semiconductor layer 404, the active region 408, and the bottomdoped semiconductor layer 412, wherein the dopant concentrationencroaches from the sidewalls of the top doped semiconductor layer 404,the active region 408, and the bottom doped semiconductor layer 412toward a center vertical axis of the LED. In an embodiment, the dopantconcentration is formed of a dopant such as Al, Mg, and Si. In anembodiment, the dopant concentration does not extend to a top surface ofthe top doped semiconductor layer 404.

In an embodiment, the LED additionally includes a p-n junction on thesidewalls of the top doped semiconductor layer 404. In an embodiment,top doped semiconductor layer 404 includes alternating n-regions and n+regions on top of one another. For example, the n− regions may have ann-dopant concentration less than the dopant concentration (e.g. Al, Mg,and Si) in the portion of the dopant concentration overlapping the n−regions. In an embodiment, the n+ regions have an n-dopant concentrationgreater than the p-dopant concentration in the portion of the dopantconcentration overlapping the n+ regions.

Referring now to FIG. 23 a flow chart is provided illustrating a methodof forming an LED including selective etching of the cladding layers andshallow doping in accordance with an embodiment. In interest of clarity,the following description of FIG. 23 is made with regard to referencefeatures found in other figures described herein. At operation 2310 anarray of mesa structures 130 is formed in the device layer 117 of a bulkLED substrate 100. At operation 2320 the cladding layers 104, 112 arethen selectively etched to reduce the respective widths of the claddinglayers 104, 112 within the mesa structures 130. At operation 2330confinement region 150 shallow doping profiles are formed alongsidewalls 131 of the mesa structures 130.

Referring now to FIG. 24 a schematic cross-sectional side viewillustration is provided of an array of mesa trenches 120 and an arrayof mesa structures 130 formed in a device layer 117 in accordance withan embodiment. The bulk LED substrate 100 illustrated in FIG. 24 may besubstantially similar to the bulk LED substrate illustrated anddescribed with regard to FIG. 1A. In the particular embodimentillustrated, mesa trenches 120 stop on or within the contact layer 102.In another embodiment, mesa trenches 120 may be formed through thecontact layer 102.

Referring now to FIG. 25, the mask layers 138 (e.g. SiN_(x)) ised forforming mesa trenches 120 may be retained on the mesa structures 130 andthe cladding layers 104, 112 are selectively etched to reduce therespective widths of the cladding layers 104, 112 within the mesastructures 130. As shown the lateral edges 105 (sidewalls) of the topcladding layer 104, and the lateral edges 113 (sidewalls) of the bottomcladding layer 112 are closer to the center vertical axis of the mesastructures than the lateral edges 107, 109, 111 of the top barrier layer106, the active layer 108, and the bottom barrier layer 110,respectively.

In an embodiment, the width of the cladding layers 104, 112 is reducedwith a wet etch operation. For example, wet HCl wet etch is inverselyselective with gallium composition, with higher gallium in thecomposition corresponding to a slower etch rate. In an embodiment,cladding layers 104, 112 have no gallium, or a lower galliumconcentration than the surrounding layers. For example, cladding layer104, 112 may be doped AlInP.

A confinement region 150 with a shallow doping profile may then bediffused into the exposed sidewalls 131 of the mesa structure 130, andoptionally any underlying layers (e.g. 102) as illustrated in FIG. 26.Where mesa structures 130 are formed on top of a contact layer 102, theconfinement region 150 shallow doping profile may extend partiallythrough or completely through a thickness of the contact layer 102. Asshown, the confinement region 150 doping profile is able to penetrate aportion of the active layer 108 by diffusing through the barrier layers110, 106 directly above and below the active layer 108. Accordingly, theshallow doping profile is capable of covering a larger volume than wouldbe possible from sidewall diffusion only, and with a lower thermal ortime budget.

Following the formation of confinement regions 150, the patterned bulkLED substrates of FIG. 26 may be processed similarly as illustrated anddescribed above with regard to FIGS. 6-11 to form an array of LEDs 195that are poised for pick up and transfer to a receiving substrate. FIGS.27A-27D are schematic cross-sectional side view illustrations of LEDs195 including selectively etched cladding layers 104, 112 andconfinement regions 150 with shallow doping in accordance withembodiments. In the embodiment illustrated in FIG. 27A, the confinementregion 150 dopant concentration may optionally extend to the top surface137 of the LED body 132 (e.g. top surface of cladding layer 104). Insuch an embodiment, the top conductive contact 182 may not extenddirectly over the confinement region 150 dopant profile in order toavoid a shunt path along the LED sidewalls. In the embodimentillustrated in FIG. 27B, a second selective etch process may beperformed after forming the confinement region 150 in order to removethe dopant profile from the lateral edges (sidewalls) 113, 105 of thecladding layers 112, 104. In this manner, the shunt path is removed.FIGS. 27C-27D are substantially similar to FIGS. 27A-27B with theaddition of the top contact layer 102. As shown, inclusion of the topcontact layer may additionally relax the alignment tolerance for the topconductive contact 182.

In an embodiment, an LED 195 includes an LED body 132 including a topcladding layer 104 doped with a first dopant type (e.g. n-type), a topbarrier layer 106 below the top cladding layer, an active layer 108below the top barrier layer 106, a bottom barrier layer 110 below theactive layer 108, and a bottom cladding layer 112 below the bottombarrier layer 110. The bottom cladding layer 112 may be doped with asecond dopant type (e.g. p-type) opposite the first dopant type. Abottom contact layer 114 may optionally be below the bottom claddinglayer 112, with the bottom contact layer 114 also doped with the seconddopant type (e.g. p-type). In an embodiment, the lateral edges(sidewalls) 113, 105 of the top cladding layer 104 and the bottomcladding layer 112 are closer to a center vertical axis 199 of the LEDbody 132 than lateral edges (sidewalls) 111, 109, 107 of the top barrierlayer 106, the active layer 108, and the bottom barrier layer 110.

In an embodiment, a confinement region 150 including a p-dopant (e.g.Mg, Zn) concentration spans the lateral edges (sidewalls) 105, 107, 109,111, 113, 115 of the top n-doped cladding layer 104, the top barrierlayer 106, the active layer 108, the bottom barrier layer 110, thebottom p-doped cladding 112 layer, and the bottom p-doped contact 114.In an embodiment, the p-dopant concentration occupies a larger volume ofthe active layer 108 than the top barrier layer 106, and the p-dopantconcentration occupies a larger volume of the active layer 108 than thebottom barrier layer 110.

Referring now to FIG. 28 a flow chart is provided illustrating a methodof forming an LED including selective etching of the cladding layers andregrowth in accordance with an embodiment. In interest of clarity, thefollowing description of FIG. 28 is made with regard to referencefeatures found in other figures described herein. At operation 2810 anarray of mesa structures 130 is formed in the device layer 117 of a bulkLED substrate 100. At operation 2820 the cladding layers 104, 112 arethen selectively etched to reduce the respective widths of the claddinglayers 104, 112 within the mesa structures 130. At operation 2830 aregrowth layer 175 is formed along sidewalls 131 of the mesa structures130.

Referring now to FIG. 29 a schematic cross-sectional side viewillustration is provided of an array of mesa trenches 120 and an arrayof mesa structures 130 formed in a device layer 117 in accordance withan embodiment. The bulk LED substrate 100 illustrated in FIG. 29 may besubstantially similar to the bulk LED substrate illustrated anddescribed with regard to FIG. 1A. In the particular embodimentillustrated a (bottom) barrier layer 110 is not illustrated. In otherembodiments, a (bottom) barrier layer 110 is included in the bulk LEDsubstrate. In the particular embodiment illustrated, mesa trenches 120stop on or within the contact layer 102. In another embodiment, mesatrenches 120 may be formed through the contact layer 102.

Referring now to FIG. 25, the mask layers 138 (e.g. SiN_(x)) used forforming mesa trenches 120 may be retained on the mesa structures 130 andthe cladding layers 104, 112 are selectively etched to reduce therespective widths of the cladding layers 104, 112 within the mesastructures 130. As shown the lateral edges 105 (sidewalls) of the topcladding layer 104, and the lateral edges 113 (sidewalls) of the bottomcladding layer 112 are closer to the center vertical axis of the mesastructures than the lateral edges 107, 109, 111 of the top barrier layer106, the active layer 108, and the bottom barrier layer 110,respectively.

In an embodiment, the width of the cladding layers 104, 112 is reducedwith a wet etch operation. For example, wet HCl wet etch is inverselyselective with gallium composition, with higher gallium in thecomposition corresponding to a slower etch rate. In an embodiment,cladding layers 104, 112 have no gallium, or a lower galliumconcentration than the surrounding layers. For example, cladding layer104, 112 may be doped AlInP.

A regrowth layer 175 is then formed on the exposed sidewalls 131 of themesa structures 130 and the underlying layers (e.g. 102) as illustratedin FIG. 31. As shown, the regrowth layer 175 at least partially fills,and may completely fill, the voids directly between the contact layer114 and active layer 108 that were created as a result of the selectiveetching operation. In an embodiment, the regrowth layer 175 is asemi-insulating layer, n-type layer, or unintentionally doped. Forexample, regrowth layer 175 may be AlIP, with Te or Fe dopants.

Following the formation of regrowth layer 175, the patterned bulk LEDsubstrates of FIG. 31 may be processed similarly as illustrated anddescribed above with regard to FIGS. 6-11 to form an array of LEDs 195that are poised for pick up and transfer to a receiving substrate. FIGS.32A-32B are schematic cross-sectional side view illustrations of LEDs195 including selectively etched cladding layers 104, 112 and a regrowthlayer 175 in accordance with embodiments. In the embodiment illustratedin FIG. 32A, the regrowth layer 175 may be exposed at the top surface137 of the LED body 132 (e.g. top surface of cladding layer 104). Insuch an embodiment, the top conductive contact 182 may not be in directcontact with the regrowth layer 175 in order to avoid a shunt path alongthe LED sidewalls. In the embodiment illustrated in FIG. 32B, a topcontact layer 102 is included. For example, the top contact layer 102may be patterned similarly as described with regard to FIG. 10. In thismanner, the shunt path is removed from the top surface 137 of the LEDbody 132. As shown, inclusion of the top contact layer 102 mayadditionally relax the alignment tolerance for the top conductivecontact 182.

In an embodiment, an LED 195 includes an LED body 132 including a topcladding layer 104 doped with a first dopant type (e.g. n-type), a topbarrier layer 106 below the top cladding layer 104, an active layer 108below the top barrier layer 106, and a bottom cladding layer 112 belowthe active layer 108. The bottom cladding layer 112 may be doped with asecond dopant type (e.g. p-type) opposite the first dopant type. Abottom contact layer 114 may be below the bottom cladding layer 112. Thebottom contact layer 114 may also be doped with the second dopant type(e.g. p-type). In an embodiment, lateral edges (sidewalls) 105, 113 ofthe top cladding layer 104 and the bottom cladding layer 112 are closerto a center vertical axis 199 of the LED body 132 than lateral edges107, 109 of the top barrier layer 106 and the active layer 108.

In an embodiment, a regrown layer 175 is formed directly on the lateraledges (sidewalls) 105, 107, 109, 113, 115 of the top cladding layer 104,the top barrier layer 106, the active layer 108, the bottom claddinglayer 112, and the bottom contact layer 114. In an embodiment, theregrown layer 175 is doped with a dopant selected from the groupconsisting of Te and Fe. In an embodiment, the regrown layer 175 fills avolume directly between the bottom contact layer 114 and the activelayer 108, and is laterally adjacent to the bottom cladding layer 112.

Referring now to FIGS. 34A-36C various process flows are illustrated formethods of forming LEDs with selectively etched layers. The particularembodiments illustrated in FIGS. 34A-36C may be utilized with bulk LEDsubstrates 400 similar to that described with regard to FIG. 37A.Additionally, the embodiments illustrated in FIGS. 34A-36C may beperformed utilizing photo electro chemical (PEC) etching techniques inwhich the bulk LED substrates 400 are submerged in an etching solution(such as KOH, HCL) and either a light is shone or a bias is applied toinitiate etching, which can be bandgap, dopant, orientation, andmaterial selective (among other possibilities). In an embodiment,shining light on the bulk LED substrate 400 targets the bandgap of aspecific layer for selective etching relative to other layers in thestructure. In an embodiment, the smallest bandgap material is selectedfor etching. In an embodiment, the smallest bandgap material (other thanin the active region, e.g. quantum well) is selected for etching.

FIGS. 33A-33D are schematic cross-sectional side view illustrations of amethod of forming LEDs with a selectively etched active region inaccordance with an embodiment. The bulk LED substrate 400 illustrated inFIG. 33A may be substantially similar to that illustrated in FIG. 37A.Mesa trenches 420 may then be formed as illustrated in FIG. 33B,followed by selective etching of the active region 408 as illustrated inFIG. 33B resulting in a reduced width of the lateral edges (sidewalls)409 of the active region 408. In an embodiment, selective etching of theactive region 408 is performed with a PEC etch. In an embodiment, theactive region 408 includes the smallest bandgap in the structure, and alaser with wavelength above the active region, and below the otherlayers in the structure causes the active region 408 to etch selectivelyin the etching solution. In accordance with an embodiment, PEC etchingadditionally removes material of the active region 408 which has beendamaged during etching of the mesa trenches 420 (e.g. during plasmaetching), which may improve device performance In an embodiment, abottom contact layer 480 (which may be similar to bottom contact layer180) is then formed over the doped semiconductor layer 412, asillustrated in FIG. 33D. Additional processing may then be performed tocomplete fabrication of the LED devices as previously described.

In an embodiment an LED structure includes an LED body with a top dopedsemiconductor layer 404 doped with a first dopant type (e.g. n-type), anactive region 408 below the top doped semiconductor layer 404, and abottom doped semiconductor layer 412 doped with a second dopant type(e.g. p-type) opposite the first dopant type, where lateral edges 409 ofthe active region 408 are closer to a center vertical axis of the LEDbody than lateral edges 405, 413 of the top doped semiconductor layer404 and the bottom doped semiconductor layer 412, respectively. In anembodiment, the top and bottom doped semiconductor layers include one ormore layers, such as a cladding layer and barrier layer.

FIGS. 34A-34C are schematic cross-sectional side view illustrations of amethod of forming LEDs with a selectively etched sacrificial region inaccordance with an embodiment. The bulk LED substrate 400 illustrated inFIG. 34A is similar to that illustrated in FIG. 33A with the addition ofsacrificial layer 486 within the doped semiconductor layer 412. Inaccordance with embodiments, sacrificial layer 486 may be a thin bulklayer (e.g. 5-50 nm thick) or a super lattice type structure. In anembodiment, sacrificial layer 486 includes InGaN. In an embodiment inwhich doped semiconductor layer 412 is p-doped, the sacrificial layer486 may likewise be p-doped.

Referring now to FIG. 34B, a bottom contact layer 480 is formed over thedoped semiconductor layer 412, and mesa trenches 420 are formed. Bottomcontact layer 480 may be formed before or after the mesa trenches 420.Referring to FIG. 34C, the sacrificial layer 486 is selectively etched,for example with PEC etching, resulting in a reduced width of thelateral edges (sidewalls) 487 of the sacrificial layer 486. Additionalprocessing may then be performed to complete fabrication of the LEDdevices as previously described. In the resultant LED device structure,the sacrificial layer 486 may function to confine current internallywithin the LED device, and prevent carriers from leaking to thesidewalls and following a shunt path along the damaged sidewallmaterials. In accordance with embodiments, the sacrificial layer may inprincipal be placed above or below the active region 408, or both. In anembodiment, p-GaN may have a higher resistivity than n-GaN, and locationof the sacrificial layer 486 within the p-doped semiconductor layer 412may potentially result in better current confinement. However,embodiments are not so limited.

In an embodiment an LED structure includes an LED body with a top dopedsemiconductor layer 404 doped with a first dopant type (e.g. n-type), anactive region 408 below the top doped semiconductor layer 404, a bottomdoped semiconductor layer 412 doped with a second dopant type (e.g.p-type) opposite the first dopant type, and a sacrificial layer 486within the bottom doped semiconductor layer 412. Lateral edges 487 ofthe sacrificial layer 486 may be closer to a center vertical axis thanlateral edges one or more of the layers in the LED body, such as lateraledges 413 of the bottom doped semiconductor layer 412, lateral edges 409the active region 408, and lateral edges 413 of the top dopedsemiconductor layer 404. In an embodiment, the sacrificial layer 486 hasa lower bandgap than materials forming the bottom doped semiconductorlayer 412 and the top doped semiconductor layer 404.

FIGS. 35A-35C are schematic cross-sectional side view illustrations of amethod of forming LEDs with a selectively etched sacrificial region inaccordance with an embodiment. FIGS. 35A-35C are substantially similarto FIGS. 34A-34C with the exception that a sacrificial layer 488 isformed within the doped semiconductor layer 404. In accordance withembodiments, sacrificial layer 488 may be a thin bulk layer (e.g. 5-50nm thick) or a super lattice type structure. In an embodiment,sacrificial layer 488 includes InGaN. In an embodiment in which dopedsemiconductor layer 404 is n-doped, the sacrificial layer 488 maylikewise be n-doped. As illustrated in FIG. 35C, selective etching ofthe sacrificial layer 488, for example, with PEC etching, may result ina reduced width of the lateral edges (sidewalls) 489 of the sacrificiallayer 488. Additional processing may then be performed to completefabrication of the LED devices as previously described.

In an embodiment an LED structure includes an LED body with a top dopedsemiconductor layer 404 doped with a first dopant type (e.g. n-type), anactive region 408 below the top doped semiconductor layer 404, a bottomdoped semiconductor layer 412 doped with a second dopant type (e.g.p-type) opposite the first dopant type, and a sacrificial layer 488within the top doped semiconductor layer 404. Lateral edges 489 of thesacrificial layer 488 may be closer to a center vertical axis than oneor more of the layers in the LED body, such as the lateral edges 413 ofthe bottom doped semiconductor layer 412, lateral edges 409 of theactive region 408, and lateral edges 405 of the top doped semiconductorlayer 404. In an embodiment, the sacrificial layer 488 has a lowerbandgap than materials forming the bottom doped semiconductor layer 412and the top doped semiconductor layer 404.

Referring now to FIGS. 36A-36C schematic cross-sectional side viewillustrations are provided of a method of forming LEDs with selectivelyetched sacrificial layers 486, 488 in accordance with embodiments. Thus,the sacrificial layers 486, 488 may be located on both sides of theactive region 408. Additional processing may then be performed tocomplete fabrication of the LED devices as previously described.

In an embodiment, an LED structure includes a sacrificial layer 486within the bottom doped semiconductor layer 412 and a sacrificial layer488 within the top doped semiconductor layer 404. Lateral edges 487 ofthe sacrificial layer 486, and lateral edges 489 of the sacrificiallayer 488 may be closer to a center vertical axis than one or more ofthe layers in the LED body, such as the bottom doped semiconductor layer412, the active region 408, and the top doped semiconductor layer 404.

FIG. 38 is a schematic cross-sectional side view illustration of an LED195 bonded to a receiving substrate 300 in accordance with anembodiment. LED 195 may be any of the LEDs described herein. Thereceiving substrate 300 may be a display backplane. As shown, the LED195 is a vertical LED, with the bottom conductive contact 180 bonded toan electrode (e.g. anode) 310 with a bonding material 312, such as asolder material. Sidewalls of the LED 195 may be surrounded by adielectric material 330. The dielectric material may serve severalfunctions such as securing the LED 195 to the receiving substrate 300,as well as providing step coverage for a top conductive layer 340, suchas a conductive oxide or conductive polymer, used to electricallyconnect the top conductive contact 182 to an electrode (e.g. cathode)320. For example, the dielectric material 330 may be an oxide, orpolymer material. The dielectric material 330, and optionally thesidewall passivation layer 170, alone or in combination, mayadditionally protect against electrical shorting between the topconductive layer 340 and sidewalls of the LED.

FIG. 39 illustrates a display system 3900 in accordance with anembodiment. The display system houses a processor 3910, data receiver3920, and one or more display panels 3930 which may include an array ofLEDs 195 bonded to a backplane (e.g. 300). The display panels 3930 mayadditionally include one or more display driver ICs such as scan driverICs and data driver ICs. The data receiver 3920 may be configured toreceive data wirelessly or wired. Wireless may be implemented in any ofa number of wireless standards or protocols.

Depending on its applications, the display system 3900 may include othercomponents. These other components include, but are not limited to,memory, a touch-screen controller, and a battery. In variousimplementations, the display system 3900 may be a wearable device (e.g.watch), television, tablet, phone, laptop, computer monitor, kiosk,digital camera, handheld game console, media display, ebook display, orlarge area signage display.

In utilizing the various aspects of the embodiments, it would becomeapparent to one skilled in the art that combinations or variations ofthe above embodiments are possible for fabricating LEDs including one ormore current confinement structures. Although the embodiments have beendescribed in language specific to structural features and/ormethodological acts, it is to be understood that the appended claims arenot necessarily limited to the specific features or acts described. Thespecific features and acts disclosed are instead to be understood asembodiments of the claims useful for illustration.

What is claimed is:
 1. A light emitting structure comprising: a bodyincluding: a first cladding layer doped with a first dopant type; abarrier layer; and an active layer between the first cladding layer andthe barrier layer; a pillar structure that protrudes from a firstsurface of the body, wherein the pillar structure includes a secondcladding layer doped with a second dopant type opposite the first dopanttype; and a confinement region including a dopant concentration spanningsidewalls of the body and the first surface of the body, wherein thedopant concentration is formed of the second dopant type and encroachesfrom the sidewalls of the body toward a center vertical axis of thelight emitting structure and from the first surface of the body towardthe active layer, and the dopant concentration laterally encroachestoward a center vertical axis of the light emitting structure within thebody past sidewalls of the pillar structure.
 2. The light emittingstructure of claim 1, wherein the pillar structure protrudes from asurface of the barrier layer, the confinement region dopantconcentration spans the surface of the barrier layer, and the dopantconcentration encroaches laterally toward the center vertical axiswithin the barrier layer past the sidewalls of the pillar structure. 3.The light emitting structure of claim 1, wherein the first dopant typeis n-type, the second dopant type is p-type, and the dopantconcentration is formed of a dopant selected from the group consistingof Mg and Zn.
 4. The light emitting structure of claim 1, furthercomprising: a conformal passivation layer formed on and spanning thesidewalls of the body, the sidewalls of the pillar structure, and asurface of the pillar structure opposite the body; an opening in theconformal passivation layer on the surface of the pillar structure; anda conductive contact formed on the surface of the pillar structure andwithin the opening of the conformal passivation layer.
 5. The lightemitting structure of claim 1, wherein the dopant concentrationencroaches further toward the center vertical axis within the barrierlayer than within the active layer and the first cladding layer.
 6. Thelight emitting structure of claim 5, further comprising a base includinga first surface, wherein the body protrudes from the first surface ofthe base, and the first surface of the base is wider than the body. 7.The light emitting structure of claim 6, wherein the dopantconcentration spans the first surface of the base, and encroaches towarda second surface of the base opposite the first surface of the base. 8.The light emitting structure of claim 7, further comprising a secondconductive contact on the second surface of the base.
 9. The lightemitting structure of claim 8, wherein the conductive contact is bondedto a contact pad on a display substrate with a solder material.
 10. Thelight emitting structure of claim 1, wherein the dopant concentrationencroaches further toward the center vertical axis within the barrierlayer and the active layer than within the first cladding layer.
 11. Thelight emitting structure of claim 10, further comprising a baseincluding a first surface, wherein the body protrudes from the firstsurface of the base, and the first surface of the base is wider than thebody.
 12. The light emitting structure of claim 11, wherein the dopantconcentration spans the first surface of the base, and encroaches towarda second surface of the base opposite the first surface of the base. 13.The light emitting structure of claim 12, further comprising a secondconductive contact on the second surface of the base.
 14. The lightemitting structure of claim 13, wherein the conductive contact is bondedto a contact pad on a display substrate with a solder material.